EP3237523B1 - Rubber composition comprising a specific hydrocarbon resin - Google Patents

Description

The invention relates to compositions, in particular for tires and more particularly to compositions comprising a specific hydrocarbon resin for improving the tack of the composition before curing.

The capacity of the rubber compositions to be tacky before curing is an essential property in the manufacture of tires. In fact, in order to make the tires, it is necessary to be able to apply the different layers of the tire on top of each other and for these layers to adhere to each other, before curing of the tire, which curing will combine the layers with each other by crosslinking. to others. This tacky property of the composition before baking is also called “raw tack” or “tack” or “green tack”.

Recent developments in tires with low rolling resistance have led tire manufacturers to substantially modify the rubber compositions of their tires. This development of low rolling resistance mixes is generally accompanied by a decrease in raw tack. In fact, the tackifying resins used to increase the raw tackiness are generally accompanied by an increase in hysteresis. The other solution for increasing the raw tack, using a brightening solvent, has the defect of releasing volatile organic compounds.

The Applicants have now shown that a particular composition comprising a specific hydrocarbon-based resin makes it possible to have very good raw tack and low rolling resistance.

The invention therefore relates to a rubber composition based on at least one diene elastomer, a reinforcing filler, a crosslinking system and a hydrocarbon resin, said hydrocarbon resin having a number average molecular mass (Mn) of between 700 and 1000. g / mol, an average molecular mass Mz within a range from 6000 to 8000 g / mol and a polymolecularity index (Ip) greater than 2.4.

Preferably, the invention relates to a composition as defined above, in which said diene elastomer is chosen from the group consisting of essentially unsaturated diene elastomers. Preferably, said diene elastomer is selected from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers and mixtures of these elastomers. More preferably, the majority diene elastomer is chosen from the group consisting of polybutadienes, copolymers of butadiene and of styrene, and natural rubber.

Preferably also, the invention relates to a composition as defined above, in which the reinforcing filler is chosen from the group consisting of silicas, carbon blacks and mixtures of the latter. More preferably, the level of reinforcing filler is within a range ranging from 5 to 200 phr, preferably from 40 to 160 phr.

Preferably, the invention relates to a composition as defined above, in which the content of said hydrocarbon resin is within a range ranging from 1 to 15 phr, preferably from 2 to 12 phr. More preferably, the level of said hydrocarbon resin is within a range ranging from 3 to 10 phr, preferably from 3 to 8 phr.

Preferably, the invention relates to a composition as defined above, in which said hydrocarbon resin has an Mn of between 800 and 1000 g / mol.

Preferably also, the invention relates to a composition as defined above, in which said hydrocarbon resin exhibits an Ip within a range ranging from 2.4 to 2.8.

Preferably, the invention relates to a composition as defined above, in which the resin is chosen from the group consisting of aliphatic hydrocarbon resins and mixtures of the latter.

According to a preferred variant, the invention relates to a composition as defined above further comprising a plasticizer system. Preferably, the plasticizer system comprises a hydrocarbon resin with a Tg greater than 20 ° C. and / or a plasticizer oil.

The invention also relates to a tire comprising a composition as defined above.

Preferably, the tire according to the invention will be chosen from the tires intended to be fitted to a two-wheeled vehicle, a passenger vehicle, or even a so-called “heavy vehicle” (that is to say metro, bus, vehicles outside the vehicle. - the road, road transport vehicles such as trucks, tractors, trailers), or even planes, civil engineering, agrarian or handling equipment.

I- Constituents of the composition

The rubber compositions according to the invention are based on at least one diene elastomer, a reinforcing filler, a crosslinking system and a specific hydrocarbon resin, said hydrocarbon resin having a number-average molecular mass (Mn) of between 700 and 1000 g / mol, an average molecular mass Mz greater than 6000 g / mol and a polymolecularity index (Ip) greater than 2.4.

By the expression “composition based on” is meant a composition comprising the mixture and / or the reaction product in situ of the various basic constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the various phases of manufacture of the composition, or during the subsequent cooking, modifying the composition as it is prepared at the start. Thus, the compositions as used for the invention can be different in the uncrosslinked state and in the crosslinked state.

In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are percentages by weight. On the other hand, any interval of values designated by the expression "between a and b" represents the range of values going from more than a to less than b (that is to say limits a and b excluded) while any range of values designated by the expression "from a to b" signifies the range of values going from a to b (that is to say including the strict limits a and b).

I-1 Diene elastomer

The compositions may contain a single diene elastomer or a mixture of several diene elastomers.

By elastomer (or “rubber”, the two terms being considered synonymous) of the “diene” type, it is recalled here that one (one or more) elastomer obtained at least in part (ie, a known manner should be understood. homopolymer or a copolymer) of diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not).

Diene elastomers can be classified into two categories: "substantially unsaturated" or "substantially saturated". In general, the term “essentially unsaturated” is understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a level of units or units of diene origin (conjugated dienes) which is greater than 15% (% by moles); it is thus that diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type do not fall within the preceding definition and can in particular be qualified as "essentially saturated" diene elastomers (content of units of weak or very weak diene origin, always less than 15%). In the category of “essentially unsaturated” diene elastomers, the term “highly unsaturated” diene elastomer is understood to mean in particular a diene elastomer having a level of units of diene origin (conjugated dienes) which is greater than 50%.

1. (a) tout homopolymère obtenu par polymérisation d'un monomère diène conjugué ayant de 4 à 12 atomes de carbone;
2. (b) tout copolymère obtenu par copolymérisation d'un ou plusieurs diènes conjugués entre eux ou avec un ou plusieurs composés vinyle aromatique ayant de 8 à 20 atomes de carbone;
3. (c) un copolymère ternaire obtenu par copolymérisation d'éthylène, d'une α-oléfine ayant 3 à 6 atomes de carbone avec un monomère diène non conjugué ayant de 6 à 12 atomes de carbone, comme par exemple les élastomères obtenus à partir d'éthylène, de propylène avec un monomère diène non conjugué du type précité tel que notamment l'hexadiène-1,4, l'éthylidène norbornène, le dicyclopentadiène;
4. (d) un copolymère d'isobutène et d'isoprène (caoutchouc butyle), ainsi que les versions halogénées, en particulier chlorées ou bromées, de ce type de copolymère.

These definitions being given, the term “diene elastomer capable of being used in the compositions according to the invention” means more particularly:

1. (a) any homopolymer obtained by polymerizing a conjugated diene monomer having 4 to 12 carbon atoms;
2. (b) any copolymer obtained by copolymerization of one or more dienes conjugated with one another or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;
3. (c) a ternary copolymer obtained by copolymerization of ethylene, of an α-olefin having 3 to 6 carbon atoms with an unconjugated diene monomer having 6 to 12 carbon atoms, such as for example the elastomers obtained from ethylene, propylene with an unconjugated diene monomer of the aforementioned type such as in particular 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene;
4. (d) a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer.

Although it applies to any type of diene elastomer, those skilled in the art of tires will understand that the present invention is preferably implemented with essentially unsaturated diene elastomers, in particular of type (a) or (b ) above.

Suitable conjugated dienes in particular are 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C1-C5 alkyl) -1,3-butadienes such as for example 2 , 3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1, 3-butadiene, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. Suitable vinyl aromatic compounds, for example, are styrene, ortho-, meta-, para-methylstyrene, the commercial mixture “vinyl-toluene”, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.

The copolymers can contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinyl aromatic units. The elastomers can have any microstructure which depends on the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the amounts of modifying and / or randomizing agent employed. The elastomers can be for example block, random, sequenced, microsequenced, and be prepared in dispersion or in solution; they can be coupled and / or starred or else functionalized with a coupling and / or starring or functionalizing agent. By function is meant here preferably a chemical group interactive with the reinforcing filler of the composition.

In summary, the diene elastomer of the composition is preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (abbreviated as "BR"), synthetic polyisoprenes (IR), natural rubber (NR), copolymers. of butadiene, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably chosen from the group consisting of butadiene-styrene (SBR) copolymers.

Thus, the invention preferably relates to compositions in which the elastomer, said diene elastomer is chosen from the group consisting of essentially unsaturated diene elastomers, and in particular from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Preferably, the majority diene elastomer is chosen from the group consisting of polybutadienes, copolymers of butadiene and of styrene, and natural rubber.

I-2 Reinforcing filler

The composition according to the invention comprises a reinforcing filler. Any type of reinforcing filler known for its capacity to reinforce a rubber composition which can be used for the manufacture of tires can be used, for example an organic filler such as carbon black, an inorganic reinforcing filler such as silica, alumina, or a cutting of these two types of filler.

Suitable carbon blacks are all carbon blacks, in particular so-called tire grade blacks. Among the latter, there will be mentioned more particularly the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example the blacks N115, N134, N234, N326, N330, N339, N347, N375, or even, according to the intended applications, blacks of higher series (for example N660, N683, N772). The carbon blacks could for example already be incorporated into an isoprene elastomer in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600 ).

As examples of organic fillers other than carbon blacks, mention may be made of organic fillers of functionalized polyvinyl as described in the applications. WO-A-2006/069792 , WO-A-2006/069793 , WO-A-2008/003434 and WO-A-2008/003435 .

The composition may contain one type of silica or a blend of several silicas. The silica used can be any reinforcing silica known to a person skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface as well as a CTAB specific surface area both less than 450 m2 / g, preferably from 30 to 400 m2 / g. As highly dispersible precipitated silicas (called “HDS”), mention will be made, for example, of the silicas “Ultrasil 7000” and “Ultrasil 7005” from the company Degussa, the “Zeosil” silicas 1165MP, 1135MP and 1115MP from the company Rhodia, “Hi-Sil EZ150G” silica from the company PPG, “Zeopol” silicas 8715, 8745 and 8755 from the Huber company, treated precipitated silicas such as, for example, the silicas “doped” with aluminum described in the application EP-A-0735088 or silicas with a high specific surface area as described in the application WO 03/16837 .

The silica preferably has a BET surface area of between 45 and 400 m2 / g, more preferably between 60 and 300 m2 / g.

These compositions may optionally also contain, in addition to coupling agents, coupling activators, inorganic fillers covering agents or more generally processing aid agents. capable in a known manner, thanks to an improvement in the dispersion of the filler in the rubber matrix and to a reduction in the viscosity of the compositions, to improve their processability in the uncured state, these agents being for example hydrolyzable silanes such as alkylalkoxysilanes, polyols, fatty acids, polyethers, primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes.

Polysulphurized silanes, called “symmetrical” or “asymmetrical” silanes are used in particular depending on their particular structure, as described for example in the applications. WO03 / 002648 (or US 2005/016651 ) and WO03 / 002649 (or US 2005/016650 ).

• x est un entier de 2 à 8 (de préférence de 2 à 5) ;
• A est un radical hydrocarboné divalent (de préférence des groupements alkylène en C1-C18 ou des groupements arylène en C6-C12, plus particulièrement des alkylènes en C1-C10, notamment en C1-C4, en particulier le propylène) ;
• Z répond à l'une des formules ci-après:
  
  dans lesquelles:
  • les radicaux R1, substitués ou non substitués, identiques ou différents entre eux, représentent un groupe alkyle en C1-C18, cycloalkyle en C5-C18 ou aryle en C6-C18 (de préférence des groupes alkyle en C1-C6, cyclohexyle ou phényle, notamment des groupes alkyle en C1-C4, plus particulièrement le méthyle et/ou l'éthyle).
  • les radicaux R2, substitués ou non substitués, identiques ou différents entre eux, représentent un groupe alkoxyle en C1-C18 ou cycloalkoxyle en C5-C18 (de préférence un groupe choisi parmi alkoxyles en C1-C8 et cycloalkoxyles en C5-C8, plus préférentiellement encore un groupe choisi parmi alkoxyles en C1-C4, en particulier méthoxyle et éthoxyle).

In particular, without the definition below being limiting, so-called "symmetrical" polysulphide silanes corresponding to the following general formula (III) are suitable:

(III) Z - A - Sx - A - Z,

in which:

• x is an integer of 2 to 8 (preferably 2 to 5);
• A is a divalent hydrocarbon radical (preferably C1-C18 alkylene groups or C6-C12 arylene groups, more particularly C1-C10, especially C1-C4 alkylene, in particular propylene);
• Z responds to one of the following formulas:
  
  in which:
  • the radicals R1, substituted or unsubstituted, identical or different from one another, represent a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl group (preferably C1-C6 alkyl, cyclohexyl or phenyl groups, especially C1-C4 alkyl groups, more particularly methyl and / or ethyl).
  • the R2 radicals, substituted or unsubstituted, identical or different from one another, represent a C1-C18 alkoxyl or C5-C18 cycloalkoxyl group (preferably a group chosen from C1-C8 alkoxyls and C5-C8 cycloalkoxyls, more preferably again a group chosen from C1-C4 alkoxyls, in particular methoxyl and ethoxyl).

In the case of a mixture of polysulfurized alkoxysilanes corresponding to formula (III) above, in particular of the usual mixtures available commercially, the average value of the “x” is a fractional number preferably between 2 and 5, more preferably close to 4. However, the invention can also be advantageously implemented, for example with disulfurized alkoxysilanes (x = 2).

As examples of polysulfurized silanes, mention will be made more particularly of polysulfides (in particular disulfides, trisulfides or tetrasulfides) of bis- ((C1-C4) -alkyl (C1-C4) silyl-alkyl (C1-C4)), such as, for example, bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulphides. Among these compounds, use is made in particular of bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT, of formula [(C2H5O) 3Si (CH2) 3S2] 2 or bis- (triethoxysilylpropyl) disulfide, abbreviated TESPD, of formula [(C2H5O) 3Si (CH2) 3S] 2. As preferred examples, mention will also be made of bis- (monoalkoxyl (C1-C4) -dialkyl (C1-C4) silylpropyl) polysulphides (in particular disulphides, trisulphides or tetrasulphides), more particularly bis-monoethoxydimethylsilylpropyl tetrasulphide as described. in the patent application WO 02/083782 (or US 2004/132880 ).

By way of coupling agent other than polysulfurized alkoxysilane, mention will also be made of bifunctional POS (polyorganosiloxanes) or else hydroxysilane polysulfides (R2 = OH in formula III above) as described in the patent applications. WO 02/30939 (or US 6,774,255 ) and WO 02/31041 (or US 2004/051210 ), or also silanes or POSs bearing azo-dicarbonyl functional groups, as described for example in patent applications WO 2006/125532 , WO 2006/125533 , WO 2006/125534 .

In the rubber compositions in accordance with the invention, the content of coupling agent is preferably between 1 and 15 phr, more preferably between 3 and 14 phr.

Those skilled in the art will understand that, as an equivalent filler of the silica described in this paragraph, a reinforcing filler of another nature, in particular organic, could be used, since this reinforcing filler is covered with a layer of silica, or else would contain functional sites, in particular hydroxyls, at its surface, requiring the use of a coupling agent to establish the bond between the filler and the elastomer.

The physical state in which the reinforcing filler is present is immaterial, whether in the form of powder, microbeads, granules, beads or any other suitable densified form.

For the needs of the invention, the level of total reinforcing filler (carbon black and / or reinforcing inorganic filler such as silica) is 5 to 200 phr, more preferably 40 to 160 phr. Below 5 phr of load, the composition could not be sufficiently reinforced, while above 200 phr of load, the composition could perform less in terms of rolling resistance.

I-3 Cross-linking system

In the composition of the invention, any type of crosslinking system known to a person skilled in the art for rubber compositions can be used.

Preferably, the crosslinking system is a vulcanization system, that is to say one based on sulfur (or on a sulfur donor agent) and on a primary vulcanization accelerator. To this basic vulcanization system can be added, incorporated during the first non-productive phase and / or during the productive phase as described later, various secondary accelerators or known vulcanization activators such as oxides. zinc, stearic acid or equivalent compounds, guanide derivatives (in particular diphenylguanidine).

Sulfur is used at a preferential rate of between 0.5 and 10 phr, more preferably between 0.5 and 5 phr, in particular between 0.5 and 3 phr.

The system for vulcanizing the composition according to the invention can also comprise one or more additional accelerators, for example compounds of the thiuram family, zinc dithiocarbamate derivatives, sulfenamides, guanidines or thiophosphates. In particular, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used, in particular accelerators of the thiazole type as well as their derivatives, accelerators of the zinc thiuram or dithiocarbamate type. These accelerators are more preferably chosen from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated "CBS"), N, N-dicyclohexyl-2-benzothiazyle sulfenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide (abbreviated "TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide (abbreviated "TBSI"), zinc dibenzyldithiocarbamate (abbreviated "ZBEC") and mixtures of these compounds. Preferably, a primary accelerator of the sulfenamide type is used.

I-4 Specific hydrocarbon resin

The composition according to the invention comprises a specific hydrocarbon resin. This hydrocarbon resin has a number-average molecular mass (Mn) of between 700 and 1000 g / mol, an average molecular mass Mz greater than 6000 g / mol and a polymolecularity index (Ip) greater than 2.4. The Mn, Mz and Ip are measured by the technique of size exclusion chromatography (SEC), according to the methods defined below.

In a manner well known to those skilled in the art, the hydrocarbon resins are prepared by polymerization. The manufacture of these resins is described in particular in “Hydrocarbon Resin” by R. Mildenberg, M. Zander, G. Collin and in particular in chapter 3. This manufacture takes place in four stages, selection and pre-treatment of the feedstocks (washing, distillation). , polymerization of feedstocks (cationic or thermal), neutralization and separation of the resin, which can be done by distillation or stripping. It is described that the synthesis parameters that can impact the characteristics of the resin are, among others, the nature of the constituents of the feedstock which is polymerized, the type of polymerization process (batch or continuous), the polymerization reaction time, the quantity of initiation reagent and the resin separation conditions.

For example, during the separation step, the resin is separated from the unreacted feedstock, which consists of molecules of low mass. Conventionally, this separation is carried out by vacuum distillation. The temperature and the pressure therefore make it possible to adjust the minimum molecular mass of the resin. Thus this step makes it possible to modify the molecular mass distribution of the resin. It is thus known to those skilled in the art that adjustments of the manufacturing parameters make it possible to obtain various characteristics for the resins prepared.

Also commercially there are many hydrocarbon resins available. These resins can have characteristics, in particular of Mn, Mz and Ip which differ according to the suppliers, and sometimes according to the batch for the same trade name. Thus, the measurement of the specific parameters of the resins, prepared or commercially available, makes it possible to choose the resin for the invention, the latter having to exhibit the specific properties of Mn, Mz and Ip described in the present application.

The macrostructure (Mw, Mn, Ip and Mz) of the hydrocarbon resin is determined by size exclusion chromatography (SEC) on the basis of ISO 16014 standards ( Determination of average molecular mass and molecular mass distribution of polymers using size exclusion chromatography ) , ASTM D5296 ( Molecular Weight Averages and molecular weight distribution of polystyrene by High performance size exclusion chromatography ), and DIN 55672 (size exclusion chromatography).

For these measurements, the resin sample is solubilized in non-antioxidant tetrahydrofuran up to a concentration of 1.5 g / l. The solution is filtered with a Teflon filter with a porosity of 0.45 μm, for example using a disposable syringe fitted with a filter. A volume of 100 μl is injected through a set of steric exclusion chromatography columns. The mobile phase is eluted with a flow rate of 1 ml / min. The columns are thermostatically controlled in an oven at 35 ° C. Detection is ensured by a refractometer thermostatically controlled at 35 ° C. The stationary phase of the columns is based on a polystyrene divinylbenzene gel with controlled porosity. The polymer chains are separated according to the size they occupy when they are dissolved in the solvent: the more they occupy a large volume, the less accessible the pores of the columns are and the shorter their elution time.

A Moore calibration curve relating the logarithm of the molar mass (logM) to the elution time (te) is carried out beforehand with polystyrene standards, and modeled by a polynomial of order 3: Log (molar mass of polystyrene) = a + b te + c te2 + d te3.

For the calibration curve, polystyrene standards with narrow molecular distributions (polymolecularity index, Ip, less than or equal to 1.1) are used. The molar mass range of these standards ranges from 160 to about 70,000 g / mol. These standards can be grouped into "families" of 4 or 5 standards having an increment of about 0.55 in log of M between each.

• Vial noir : Mp = 1 220, 4 850, 15 500 et 67 500 g/mol.
• Vial bleu : Mp = 376, 3 470, 10 400, 46 000 g/mol.
• Vial jaune : Mp = 266, 1 920, 7 200, 28 000 g/mol.
• PS162 : Mp = 162 g/mol.

It is possible to use certified standard kits (ISO 13885 and DIN 55672) such as for example the vials kits from the company PSS (polymer standard service, reference PSS-pskitr1l-3), as well as an additional standard PS of Mp = 162 g / mol (Interchim, reference 178952). These kits come in the form of 3 vials each containing a family of standard polystyrene in suitable quantities:

• Black vial: Mp = 1,220, 4,850, 15,500 and 67,500 g / mol.
• Blue vial: Mp = 376, 3,470, 10,400, 46,000 g / mol.
• Yellow vial: Mp = 266, 1920, 7200, 28000 g / mol.
• PS162: Mp = 162 g / mol.

The number-average molar masses (Mn), mass (Mw), Mz, and the polydispersity of the resin analyzed are calculated from this calibration curve. This is why we speak of molar masses relating to a polystyrene calibration.

For the calculation of the mean masses and of the Ip, the integration limits of the elution of the product are defined on the chromatogram corresponding to the injection of the sample. The refractometric signal defined between the 2 integration terminals is "cut" every second. For each of the “elementary cuts”, the elution time ti and the area of the signal from detector Ai are recorded.

$$\mathit{Mn}=\frac{{\displaystyle \sum \mathit{Ai}}}{{\displaystyle \sum \frac{\mathit{Ai}}{\mathit{Mi}}}}$$

$$\mathit{Mw}=\frac{{\displaystyle \sum \mathit{Ai}\ast \mathit{Mi}}}{{\displaystyle \sum \mathit{Ai}}}$$

dans lesquelles Ai est l'amplitude du signal du détecteur refractométrique correspondant à la masse Mi et au temps d'élution ti.It is recalled here that: Ip = Mw / Mn with Mw average molecular mass by weight, and Mn molecular mass by number. It is also recalled that the masses Mw, Mn and Mz are average masses calculated according to the formulas below: $$\mathit{MZ}=\frac{{\displaystyle \sum \mathit{Have}\ast {\mathit{Mid}}^2}}{{\displaystyle \sum \mathrm{Have}\ast \mathrm{Mid}}}$$

$$\mathit{Mn}=\frac{{\displaystyle \sum \mathit{Have}}}{{\displaystyle \sum \frac{\mathit{Have}}{\mathit{Mid}}}}$$

$$\mathit{Mw}=\frac{{\displaystyle \sum \mathit{Have}\ast \mathit{Mid}}}{{\displaystyle \sum \mathit{Have}}}$$

in which Ai is the amplitude of the signal from the refractometric detector corresponding to the mass Mi and to the elution time ti.

The equipment used for the SEC measurement is a liquid chromatography line, for example the Alliance 2690 line from WATERS comprising a pump, a degasser and an injector; a differential refractometer (for example the 2410 refractometer from WATERS), a data acquisition and processing software, for example the EMPOWER software from WATERS, a column oven, for example the WATERS “columns Heater Module” and 4 mounted columns in series in the following order: Number Mark Molar mass range (g / mol) Length (mm) Internal diameter (mm) Particle size (µm) Commercial designation References (indicative) Columns 1 and 2 Polymer Laboratories 200 - 400,000 300 7.5 5 MIXED-D PL1110-6504 Columns 3 and 4 Polymer Laboratories 200 - 30,000 300 7.5 3 MIXED-E PL1110-6300

The commercial resins below were analyzed with the method described above to determine their characteristics, Table 1 summarizes the results obtained. <b><u> Table 1 </u></b> Mn (g / mol) Mz (g / mol) Ip Resin 1 (1) 1830 7200 2.1 Resin 2 (2) 1344 8835 2.6 Resin 3 (3) 895 4228 2 Resin 4 (4) 586 5200 3 Resin 5 (5) 341 597 1.3 Resin 6 (6) 1370 7250 2.3 Resin 7 (7) 901 7076 2.6 (1) Resin 1: "R 7578 P" from the company SI group
(2) Resin 2: “Piccotac 1105-E” from the company Eastman
(3) Resin 3: “HIKOREZ A-1100” from the company Kolon
(4) Resin 4: “Novares TD 120” from Rutgers
(5) Resin 5: “Novares TL 10” from Rutgers
(6) Resin 6: “Escorez 1102 type 1” from Exxon
(7) Resin 7: “Escorez 1102 type 2” from the company Exxon

Table 1, by the analysis of commercial resins, shows that only resin 7 satisfies the criteria of the resin useful for the needs of the invention, in particular in comparison with resin 6, which another type of resin although bearing the same commercial reference from the same company.

Preferably, the resin has a glass transition temperature, Tg, within a range ranging from -50 ° C to 100 ° C, more preferably from 40 to 60 ° C. The Tg is measured according to ASTM D3418 (1999).

Preferably, the resin has a softening point in the range from 0 to 160 ° C, preferably from 90 to 110 ° C. The softening point is measured according to the ISO 4625 standard ("Ring and Ball" method).

Preferably, the resin has an Mn within a range ranging from 800 to 1000 g / mol.

Preferably, the resin has an Mz within a range ranging from 6000 to 8000 g / mol.

Preferably, the resin has an Ip within a range ranging from 2.4 to 2.8.

The resin useful for the purposes of the invention can be chosen from natural or synthetic resins. Among the synthetic resins, it may be preferably chosen from thermoplastic aliphatic or aromatic hydrocarbon resins or else of the aliphatic / aromatic type, ie based on aliphatic and / or aromatic monomers.

Suitable aromatic monomers are, for example, styrene, alpha-methylstyrene, ortho-, meta-, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene. , vinylnaphthalene, any vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic monomer is styrene or a vinylaromatic monomer obtained from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinyl aromatic monomer is the minority monomer, expressed as a molar fraction, in the copolymer considered.

According to a particularly preferred embodiment, the resin useful for the needs of the invention is chosen from the group consisting of aliphatic hydrocarbon resins and mixtures of the latter and in particular from resins of homopolymers or copolymers of cyclopentadiene (abbreviated CPD ) or dicyclopentadiene (abbreviated DCPD), resins of homopolymers or copolymers of C5 cut and mixtures of the latter.

Preferably, the resin content is within a range ranging from 1 phr to 15 phr, preferentially from 2 to 12 phr, even more preferably from 3 to 10 phr, in particular from 3 to 8 phr. Indeed, below 1 phr of the resin useful for the needs of the invention, the composition could exhibit tackiness problems and therefore of industrial processability, while above 15 phr, the resin could modify the stiffness and glass transition temperature properties of the composition.

I-5 Other possible additives

The rubber compositions in accordance with the invention optionally also include all or part of the usual additives usually used in the elastomer compositions intended in particular for the manufacture of treads, such as, for example, pigments, protective agents such as anti-waxes. -ozone, chemical anti-ozonants, anti-oxidants, plasticizers other than those previously described, anti-fatigue agents, reinforcing resins, acceptors (for example phenolic novolak resin) or methylene donors (for example HMT or H3M).

The composition according to the invention can also comprise a plasticizer system. This plasticizer system may be composed of a hydrocarbon resin with a Tg greater than 20 ° C., in addition to the specific hydrocarbon resin described above, and / or a plasticizer oil.

Of course, the compositions in accordance with the invention can be used alone or as a blend (i.e., as a mixture) with any other rubber composition which can be used for the manufacture of tires.

It goes without saying that the invention relates to the rubber compositions described above both in the so-called "raw" or uncrosslinked state (ie, before curing) and in the so-called "cured" or crosslinked state, or else vulcanized ( ie, after crosslinking or vulcanization).

II- Preparation of rubber compositions

The compositions are manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first thermo-mechanical working or mixing phase (sometimes referred to as a “non-productive” phase) at high temperature, up to a maximum temperature of between 110 ° C and 190 ° C, preferably between 130 ° C and 180 ° C, followed by a second phase of mechanical work (sometimes called "productive" phase) at a lower temperature, typically less than 110 ° C, for example between 60 ° C and 100 ° C, finishing phase during which the crosslinking system is incorporated or vulcanization; such phases have been described for example in the applications EP-A-0501227 , EP-A-0735088 , EP-A-0810258 , WO00 / 05300 or WO00 / 05301 .

The first phase (non-productive) is preferably carried out in several thermomechanical steps. During a first step, the elastomers, the reinforcing fillers, the hydrocarbon resin (and optionally the coupling agents and / or other ingredients with the exception of a suitable mixer such as a conventional internal mixer) are introduced. of the crosslinking system), at a temperature between 20 ° C and 100 ° C and, preferably, between 25 ° C and 100 ° C. After a few minutes, preferably from 0.5 to 2 min and a rise in temperature to 90 ° C to 100 ° C, the other ingredients (that is to say, those which remain if all have not been put at the start) are added all at once or in parts, with the exception of the crosslinking system during mixing ranging from 20 seconds to a few minutes. The total mixing time, in this non-productive phase, is preferably between 2 and 10 minutes at a temperature less than or equal to 180 ° C, and preferably less than or equal to 170 ° C.

After cooling the mixture thus obtained, the crosslinking system is then incorporated at low temperature (typically less than 100 ° C.), generally in an external mixer such as a roller mixer; the whole is then mixed (productive phase) for a few minutes, for example between 5 and 15 min.

The final composition thus obtained is then calendered, for example in the form of a sheet or of a plate, in particular for a characterization in the laboratory, or else extruded, to form for example a rubber profile used for the manufacture of semi-solid. finishes for tires. These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art, with the advantage of the invention, namely a good tack of the layers to one another before curing of the tire.

The crosslinking (or baking) is carried out in a known manner at a temperature generally between 130 ° C and 200 ° C, under pressure, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the baking temperature , the crosslinking system adopted, the crosslinking kinetics of the composition in question or the size of the tire.

The examples which follow illustrate the invention without, however, limiting it.

III- Examples of embodiment of the invention 111-1 Preparation of examples

In the examples which follow, the rubber compositions were produced as described above.

III-2 Characterization of the examples

In the examples, the rubber compositions are characterized before and / or after curing as indicated below.

- Bare tights (or tack):

Tack is the ability of an assembly of unvulcanized mixtures to resist pulling stress.

A test device based on the probe tack tester (ASTM D2979-95) is used for the measurement of the bare tack (tack). An Instron traction machine with a fixed metal jaw and a movable metal jaw is used. A first test piece made up of a 3mm thick mixing film is glued to the fixed jaw. A second test piece made of a 3mm thick film of mixture is glued to the movable jaw. The mixing films are bonded to the surface of the metal jaws with double-sided adhesive (Tesafix® 4970).

For the preparation of the mixture specimens, the mixture films are obtained by calendering to a thickness of 3 mm. The test pieces are cut using a cookie cutter with a diameter of 1 cm.

The principle of the measurement consists in bringing the two mixing films into contact for 5 seconds by applying a compressive force of 40 N. After this contact phase, they are separated by driving the cross member of the traction machine. The speed of movement of the crosspiece in this tearing phase is 1mm / s. Crosshead displacement and force are measured continuously as a function of time during the contact and breakout phases.

The raw tack result is the measurement of the maximum force reached during the pullout.

The results are expressed in base 100, that is to say that the value 100 is arbitrarily assigned to the best control, in order to then compare the raw tack of the different solutions tested, the higher the value, the greater the raw tack. is strong.

- Dynamic properties (after cooking):

The dynamic properties G * and tan (δ) max are measured on a viscoanalyst (Metravib V A4000), according to standard ASTM D 5992 - 96. The response of a sample of vulcanized composition is recorded (cylindrical test piece of 4 mm d ' thickness and section 400 mm2), subjected to a sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under variable temperature conditions, in particular at 60 ° C, according to standard ASTM D 1349 - 99. A peak-to-peak strain amplitude sweep from 0.1 to 50% (forward cycle), then from 50% to 1% (return cycle). The results used are the complex dynamic shear modulus (G *) and the loss factor (tan δ). For the return cycle, we indicate the maximum value of tan δ observed (tan (δ) max), as well as the difference in complex modulus (ΔG *) between the values at 0.1% and at 50% deformation (effect Payne). For the value of tan (δ) max at 60 ° C, the lower the value, the lower the composition will have a low hysteresis and therefore a low rolling resistance. The results are expressed in base 100, that is to say that the value 100 is arbitrarily assigned to the best control, to then compare the tan (δ) max at 60 ° C (that is to say the hysteresis - and therefore the rolling resistance) of the different solutions tested.

III-3 Examples

The compositions are manufactured with an introduction of all the constituents on an internal mixer, with the exception of the vulcanization system. The vulcanizing agents (sulfur and accelerator) are introduced into an external mixer at low temperature (the cylinders constituting the mixer being at approximately 30 ° C.).

The examples presented in Table 2 are intended to compare the different rubber properties of control compositions (C1 to C7) with a C8 composition in accordance with the invention. The properties measured before and after baking are presented in Table 3. <u> Table 2 </u> C1 C2 C3 C4 C5 C6 C7 C8 NR (1) 25 25 25 25 25 25 25 25 BR (2) 75 75 75 75 75 75 75 75 Carbon black (3) 65 65 65 65 65 65 65 65 Resin 1 (4) - 5 - - - - - - Resin 2 (5) - - 5 - - - - - Resin 3 (6) - - - 5 - - - - Resin 4 (7) - - - - 5 - - - Resin 5 (8) - - - - - 5 - - Resin 6 (9) - - - - - - 5 - Resin 7 (10) - - - - - - - 5 Antioxidant (11) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Stearic acid (12) 3 3 3 3 3 3 3 3 ZnO (13) 4 4 4 4 4 4 4 4 Accelerator (14) 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 Soluble sulfur 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 (1) NR: natural rubber
(2) BR: polybutadiene
(3) Carbon black Grade ASTM N375 (Cabot company)
(4) Resin 1: “R 7578 P” from the company SI group
(5) Resin 2: “Piccotac 1105-E” from the company Eastman
(6) Resin 3: “HIKOREZ A-1100” from the company Kolon
(7) Resin 4: “Novares TD 120” from Rutgers
(8) Resin 5: “Novares TL 10” from Rutgers
(9) Resin 6: “Escorez 1102 type 1” from the company Exxon
(10) Resin 7: “Escorez 1102 type 2” from the company Exxon
(11) N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (Santoflex 6-PPD) from the company Flexsys and Anti-ozone wax
(12) “Pristerene 4931” stearin from Uniqema
(13) Industrial grade zinc oxide - Umicore company
(14) N-cyclohexyl-2-benzothiazol-sulfenamide (“Santocure CBS” from the company Flexsys) C1 C2 C3 C4 C5 C6 C7 C8 Bareback pantyhose (base 100) 32 100 61 48 40 39 63 87 Tan (delta) max at 60 ° C (base 100) 100 118 98 100 114 101 98 101

Compared to the control compositions, it is noted that the composition C8, in accordance with the invention, exhibits a raw tackiness / improved hysteresis compromise compared to all the controls and in particular compared to the control C2, which, if it exhibits a better raw tacky performance that composition C8 according to the invention also exhibits greater hysteresis, penalizing rolling resistance. We can also note the great difference between compositions C7 and C8, indicating that depending on the manufacturing version of the same resin, here “Escorez 1102”, the properties can vary significantly, depending on the precise characteristics of Mn, Mz and Ip of the resin. Here, the control composition C7 exhibits a hysteresis comparable to the composition in accordance with the invention but a much poorer raw tackiness. Composition C8 of the invention therefore has the best performance compromise between raw tack and rolling resistance, with a level of hysteresis as low as control C1 without resin, and a high level of raw tack.

Claims (14)

1. Rubber composition based on at least one diene elastomer, a reinforcing filler, a crosslinking system and a hydrocarbon-based resin, said hydrocarbon-based resin having a number-average molecular weight (Mn) of between 700 and 1000 g/mol, an average molecular weight Mz within a range extending from 6000 to 8000 g/mol and a polydispersity index (PI) of greater than 2.4.
2. Composition according to Claim 1, in which said diene elastomer is selected from the group consisting of essentially unsaturated diene elastomers.
3. Composition according to any one of the preceding claims, in which said diene elastomer is selected from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers and mixtures of these elastomers.
4. Composition according to any one of the preceding claims, in which the predominant diene elastomer is selected from the group consisting of polybutadienes, copolymers of butadiene and styrene, and natural rubber.
5. Composition according to any one of the preceding claims, in which the reinforcing filler is selected from the group consisting of silicas, carbon blacks and the mixtures thereof.
6. Composition according to any one of the preceding claims, in which the content of reinforcing filler is within a range extending from 5 to 200 phr and preferably from 40 to 160 phr.
7. Composition according to any one of the preceding claims, in which the content of said hydrocarbon-based resin is within a range extending from 1 to 15 phr and preferably from 2 to 12 phr.
8. Composition according to Claim 7, in which the content of said hydrocarbon-based resin is within a range extending from 3 to 10 phr and preferably from 3 to 8 phr.
9. Composition according to any one of the preceding claims, in which said hydrocarbon-based resin has an Mn of between 800 and 1000 g/mol.
10. Composition according to any one of the preceding claims, in which said hydrocarbon-based resin has a PI within a range extending from 2.4 to 2.8.
11. Composition according to any one of the preceding claims, in which the resin is selected from the group consisting of aliphatic hydrocarbon-based resins and mixtures thereof.
12. Composition according to any one of the preceding claims, additionally comprising a plasticizing system.
13. Composition according to the preceding claim, in which the plasticizing system comprises a hydrocarbon-based resin with a Tg of greater than 20°C and/or a plasticizing oil.
14. Tyre comprising a composition according to any one of Claims 1 to 13.